The use of two component cartridge systems is well known for the storage, metering and mixing of two component reactive chemical systems such as epoxies, polyurethanes, acrylics, silicones, polysulfides and polyesters. It is also well known that, for environmental reasons, cartridge systems including sausage type packages with thin plastic/foil laminate membrane walls are used to contain such chemicals. These packages are fitted within and supported by a cartridge like structure while the contents are dispensed. When depleted, the sausage type packages may be disposed of, while the whole (or majority) of the supporting cartridge structure can be reused.
It is within this field of sausage type package use that certain problems are seen to arise. For example, U.S. Pat. Nos. 5,332,122 and 5,501,368 teach containers for flowable substances. These containers require packages fabricated from flexible plastic foil/laminate sheets. For a given package, the flexible plastic foil/laminate sheet is folded to form a tube and then partially overlapped and welded together such that, along the weld length, the now double layer seam is thicker and less flexible than the rest of the package wall and is subject to potential leakage due to weld failure. Moreover, the aforementioned container tube fabrication takes place as the first stage of a complex and continuous fabrication, filling and closing process, the process continues after the initial closing of the tube with the immediate chemical filling of the tube as the second stage. The third stage involves the dividing off and closing of the, now, filled tube into volumetrically controlled lengths. At the division points, the filled tube diameter is reduced all the way to the tube axis, which results in considerable wrinkling of the tube wall prior to being closed by a crimped ring. Such crimped ring closures often fail to achieve an effective seal due to the incompressibility of the membrane and of the wrinkled overlaps which, themselves, tend to form leak paths under pressure. For the same reasons, the necessary sealing of the wrinkled tube wall against a front outlet is another failure area.
In addition, at a time just prior to the package use and after it has been placed within a reusable cartridge support structure, the package outlet end must be opened. This is done by cutting behind the crimped ring closure of the package. This opening of the package outlet end allows the package to settle within the reusable cartridge, adjusting its outer shape to conform to that of the internal diameter of the supporting structure. In doing so, air is induced into the package, particularly with lower viscosity chemicals. Thus, as air within a metering package causes the content to be non-hydraulic and therefore compressible, both the start and the stop of each of the two metered flows go out of synchronization relative to each other, which can result in an xe2x80x9coff ratioxe2x80x9d mixture when being processed through a static mixer. Furthermore, at the end of the discharge stroke, this can also lead to an unacceptable residual volume of chemical left within the center of the collapsed package due to incomplete compaction as a result of the membrane having been scraped off the outer supporting structure wall, folded and compacted in a more or less ring shaped fashion.
Alternatively, if a fabricated membrane container with a longitudinal seam is used for a package, problems arise in particular at the outlet of the package. One proposal, according to U.S. Pat. No. 5,647,510, provides, at the outlet end, an outlet piece to which the straight end of the membrane container wall is adhered. This adhesion process, however, is difficult to achieve in a leak proof and reliable fashion.
Starting from the aforementioned prior art, it is an object of the present invention to provide a thin wall membrane package which overcomes the above mentioned drawbacks, and provides a proper sealing and closure of the outlet end.
A further object is to avoid the problems arising from the fabricated sausage type package with longitudinal seams and a rear end closure. Thus, according to one aspect of the present invention, a package assembly is provided including an integrally formed, uniform and seamless thin flexible membrane wall container so as to avoid any chance of seam joint or rear end closure failure.
A further object is to provide for a package with easy handling and assembling properties and which improves, in particular, the attachment of a dynamic mixer.
Above all, another aspect of the present invention is directed at improving and/or eliminating the highly complex and necessarily combined fabrication and filling process, which entails high initial capital investment and is only economically viable for long production runs that can absorb the high xe2x80x9csetting upxe2x80x9d costs prior to each production run. Hence, an environmentally advantageous package is proposed with the major advantages of being fillable by existing conventional cartridge filling methods, yet avoiding the entrapment of air within the liquid chemical content.